Civil Engineering Reference
In-Depth Information
mainly used for putting up wallpaper. The paste can also be made of potato
starch or rye flour.
Cellulose glue is not attacked by micro-organisms, even in damp conditions.
Soya glue and flour paste should be restricted in their use to dry areas. The
solvent used for natural resin products and cellulose glue is turpentine or pure
alcohol, the latter up to as much as 70 per cent.
These glues originate from renewable plant sources. Products usually cause
little pollution in their manufacture, the exception being cellulose glue, the
main which is methyl cellulose. The production of methyl cellulose involves
chlorinated hydrocarbons such as methyl chloride, methyl iodide and dimethyl
sulphate. Possible alcohol solvents can be produced from the plants them-
selves.
During building use, these products do not cause problems. Waste from glue
can cause the growth of algae in water systems, but this risk is insignificant as
the amount of glue in question is usually small. Glues with strong fungicides
added are an exception to this. Materials glued together with plant glue can
usually be energy recycled in normal incinerators or deposited without special
restrictions.
Starch glue
Starch glue or carbohydrate glue is based on vegetable starch. The paste is relatively
weak and is used primarily for pasting paper and wallpaper, but it can also be used for
lighter woodwork and is used in the USA for gluing plywood. Potato flour paste and flour
paste are starch glues.
Potato starch is dissolved in warm water and mixed to a porridge. The porridge is
allowed to stand for 10 minutes so that the water is absorbed by the grains of starch and
thickens. Afterwards cold water is added to make it easy to stir. The mixture is then boiled
and thickens more; water is added until a workable consistency is obtained. The glue must
not be used until it is cold.
If the paste has to stand for a time a little alum is added to prevent it turning sour. If
hydrochloric acid is added to the potato starch, dextrine is formed, which gives a glue of
a far higher durability. Dextrine is also used in fillers containing gypsum.
Flour from wheat, maize or rye is used to make flour paste, which is stirred in warm
water to a white sauce, adding water carefully so that the paste does not become lumpy.
The mixture can also be sieved. This glue must also be used cold, and it is a definite
advantage to add alum. Paste from wheat flour is mostly used to stick paper and wallpa-
per. In commercial products, fungicides are often added. Rye flour paste is a little stronger
and is used for sticking paper on hessian, linoleum and wallpapers, and as a filler. Sago
flour is used for the gluing of wood.
Rye flour filler
Emulsion filler based on rye flour is based on 9 dl boiled linseed oil, 9 dl water and about
0.5 kg chalk. This is gently mixed and allowed to stand for half an hour without being
stirred. A pinch of rye flour is sprinkled on the mixture and thoroughly stirred in. More
chalk, which acts as the filler, is added, until the mixture has the consistency of porridge.
Pigments such as umbra and ochre can be used to colour it.
